UNIVERSITY    OF    CALIFORNIA     AGRICULTURAL    EXPERIMENT   STATION 
COLLEGE   OF  AGRICULTURE  BENJ    'DE  WHEELER-  '"— 

THOMAS    FORSYTH    HUNT,    Dean  an d  Director 
BERKELEY  H.    E.    VAN    NORMAN,    Vice-Director    and    Dean 

University  Farm   School 


CIRCULAR  No.  173 

(Revised) 
August,  1918 

THE  CONSTRUCTION  OF  THE 
WOOD-HOOP  SILO 

By  J.  E.  STILES  and  J.  B.  DAVIDSON 


The  purpose  of  this  circular  is  to  explain  briefly,  yet  somewhat 
in  detail,  the  construction  of  the  wood-hoop  silo.  Although  prepared 
specifically  to  sunply  the  demand  for  this  information,  prospective  silo 
builders  will  no  doubt  desire  a  statement  concerning  the  merits  and 
limitations  of  this  type  of  silo.  For  information  concerning  the  size 
of  silo  to  build,  its  location,  and  silage  feeding,  the  reader  is  referred 
to  this  station's  Circular  No.  138,  "The  Silo  in  California  Agricul- 
ture," and  to  Bulletin  No.  282,  "Trials  with  California  Silage  Crops 
for  Dairy  Cows. ' ' 

THE  WOOD-HOOP  SILO 

The  essential  requirements  of  any  silo  are  three  in  number,  viz. : 

1.  An  impervious  wall  to  exclude  the  air  and  retain  the  moisture 
of  the  silage. 

2.  A  smooth  perpendicular  wall,  which  will  permit  the  silage  to 
settle  properly. 

3.  Sufficient  strength  and  rigidity  to  withstand  the  bursting  pres- 
sure of  the  silage  from  within,  and  the  force  of  the  wind  from  without. 

The  wood-hoop  silo  will  furnish  all  of  these  essentials  with  a  mini- 
mum expenditure  for  materials.  It  has  not  the  durability  of  masonry 
or  heavier  silos,  nor  the  convenience  of  many  commercial  silos,  except 
that  in  smaller  sizes  it  can  be  readily  moved  from  one  foundation  to 
another,  a  feature  of  some  advantage  to  tenant  farmers.  It  is  not 
the  best  silo  from  the  constructional  standpoint,  but  it  may  be  the  best 
from  the  economic,  as  it  is  the  cheapest,  and  furthermore  can  be  farm- 
made  from  standard  building  materials  sold  at  local  lumber  yards. 


The  wood-hoop  silo  is  one  of  the  oldest  types  of  silos  in  use,  having 
been  used  in  different  parts  of  the  country  for  more  than  twenty 
3^ears.  It  is  not  to  be  considered  an  experimental  structure  in  any 
sense.  Although  it  may  be  considered  a  temporary  silo,  its  durability 
will  depend  upon  the  selection  of  material  and  the  workmanship  used. 
Such  silos  have  been  known  to  be  in  use  after  fifteen  years. 


Fig.  1. — The  wood-hoop  silo  at  the  University  Farm,  Davis;   12  feet  in  diameter 
by  36  feet  high,  with  2-foot  pit.     Cost  of  materials  (in  1917),  $140. 


Prepared  woornq- 

/4PlTCtt 


Fig.  2. — Plan  and  elevation  of  wood-hoop  silo.     (See  page  16  for  spacing  of  hoops 
for  various  sizes  of  silos.) 


CONSTRUCTION 

The  construction  of  the  wood-hoop  silo  is  simple,  for  there  are  but 
three  essential  parts  to  the  silo  proper:  (a)  the  hoops  which  resist  the 
bursting  pressure  of  the  silage;  (b)  the  diagonal  braces  between  the 
hoops  which  are  needed  to  give  the  silo  rigidity;  and  (c)  the  lining  of 
tongue  and  groove  staves. 

Shrinkage  of  the  Staves. — No  provision  is  made  to  take  up  the 
shrinkage  of  the  staves  which  must  necessarily  happen  in  dry  weather 
when  the  silo  is  empty.  It  has  been  fully  demonstrated,  however,  that 
if  the  fiber  has  not  been  crushed,  wood  will  always  occupy  the  same 


-«VWfa««. 


Fig.  3. — Laying  out  the  foundation. 

volume  with  a  certain  moisture  content.  As  each  stave  is  nailed  to 
the  hoops  the  shrinkage  is  evenly  distributed  and  does  not  materially 
affect  the  rigidity  of  the  silo.  Dry  lumber  should  be  used,  however, 
in  laying  up  the  wall  to  insure  a  perfectly  tight  wall  when  moist. 


FOUNDATION 

Under  usual  conditions  concrete  makes  the  best  foundation  for  the 
wood-hoop  silo.  When  frost  does  not  interfere  the  foundation  may 
be  simply  a  ring  of  concrete,  twelve  inches  wide,  deep  enough  to  get 
a  good  bearing,  or  about  twelve  inches,  and  high  enough  to  place  the 
silo  six  inches  or  more  above  the  ground. 

Forms. — In  making  the  foundation  wall,  lay  off  two  circles  from  a 
common  center,  as  shown  in  Fig.  3.    The  radius  of  the  smaller  circle 


should  be  four  inches  less  than  the  radius  of  the  silo  and  the  radius 
of  the  larger  circle  eight  inches  more.  Stakes  may  now  be  driven  on 
the  line  inside  the  inner  circle  and  outside  the  outer  circle.  The 
stakes  are  then  lined  with  thin  lumber  or  hoop  material,  as  shown  in 
Fig.  4,  using  care  to  make  level  the  top  of  the  form,  so  prepared.  A 
trench  is  then  dug  between  the  stakes  so  lined,  twelve  to  fifteen  inches 
deep,  depending  upon  the  condition  of  the  soil,  and  the  form  is  ready 
for  filling  with  concrete. 

Concrete. — The  concrete  should  be  made  of  a  mixture  of  about  one 
part  cement,  three  parts  sand,  and  four  parts  gravel  or  broken  stone. 
If  mixed  sand  and  gravel  of  good  quality  is  available  a  mixture  of 
one  part  cement  to  six  parts  mixed  gravel  may  be  used.    The  concrete 


CR055-  SECTION 
OF  FOUNDATION 


Fig.  4. — Form  ready  for  concrete. 


should  be  placed  so  wet  that  it  can  be  poured  from  a  bucket  easily 
and  should  be  given  at  least  a  day  to  set  before  erecting  the  silo. 
Concrete  poured  in  this  condition  needs  very  little  tamping.  Smooth 
off  the  top  of  the  concrete  level  with  the  form  and  trowel  the  surface 
smooth. 

Bolts. — Six  %  X  12  inch  bolts,  for  small  silos,  twelve  feet  or  less 
in  diameter,  and  eight  bolts  for  large  silos,  should  be  set  in  the  soft 
concrete,  equidistant  from  one  another,  and  standing  about  one  inch 
above  the  width  of  the  hoop  material  above  the  concrete.  These  bolts 
must  be  placed  accurately  on  the  circle  so  that  they  will  come  through 
the  middle  of  the  hoop  when  placed  on  the  concrete  (see  Fig.  4,  cross- 
section  of  foundation).  These  can  be  easily  set  correctly  by  cutting 
a  notch  in  the  side  of  the  sweep  shown  in  Fig.  4  and  setting  each  bolt 
by  the  notch.  Have  the  notch  half  the  diameter  of  the  silo,  plus 
%-inch  allowance  for  the  thickness  of  the  wall,  plus  one-half  the  thick- 
ness of  the  proposed  hoop,  away  from  the  pin  at  the  center.     If  a 


12-foot  silo  is  to  be  made  with  hoops  six  bands  thick,  of  %-inch 
material,  then  the  notch  would  be  6'  +  %"  -f  1%"  =*=  6'  2"  from  the 
center  pin.  The  most  satisfactory  bolts  are  made  of  pieces  of  %-inch 
iron,  14  inches  long,  threaded  on  one  end  and  bent  at  right  angles 
two  inches  from  the  other  end.  These  bolts  will  not  turn  in  the 
concrete. 

HOOPS 

Material. — The  material  for  the  hoops  may  be  any  thin  lumber 
free  from  knots,  dressed  to  size,  %-inch  thick  and  2%  to  4  inches  wide. 
Sugar  pine,  redwood,  white  cedar,  and  Douglas  fir  have  all  been  used 
successfully.  Batten  stock  which  can  be  procured  in  all  yards  is  quite 
satisfactory  for  the  smaller  silos.  For  silos  larger  than  ten  feet  in 
diameter  material  %  X  3%  inches  is  more  satisfactory. 

MAKING  THE  HOOPS 

The  first  step  in  making  the  hoops  is  to  prepare  a  fairly  smooth 
floor  of  2-inch  material,  about  two  feet  larger  in  diameter  than  that 
of  the  proposed  silo.  This  floor  is  usually  a  temporary  floor  made  of 
2-inch  -planks  laid  across  three  or  four  pieces  of  2  X  4-inch  material, 
as  shown  in  Fig.  5,  and  nailed  down.  The  next  step  is  to  build  the 
master  hoop  or  form  in  which  the  hoops  are  made.  First  describe  a 
circle  on  the  floor  with  a  radius  equal  to  one-half  the  inside  diameter 
of  the  silo  plus  %  inch  allowance  for  the  thickness  of  the  staves 
plus  the  thickness  of  the  hoop,  plus  the  thickness  of  three  bands 
of  the  hoop  material  making  up  the  master  hoop.  This  line  will 
come  at  the  outside  of  the  master  hoop.  If  a  silo  twelve  feet  in 
diameter  with  hoops  six-ply  thick  is  to  be  made,  then  the  two  nails 
in  the  stick  to  be  used  as  a  compass  will  be  6'  +  %"  +  (%"  X  6)  + 
(%"  X  3)  =  total  6'  414"  apart.  One  nail  is  driven  in  the  center  of 
the  floor  and  the  other  scratches  the  line  as  the  stick  is  swung  around. 

A  number  of  blocks  about  10  inches  long  are  now  cut  from  2X3 
inch  or  2  X  4  inch  material,  according  as  the  hoop  material  is  3  or  4 
inches  wide,  with  one  square  end  and  one  sloping  end.  See  blocks 
around  outside  of  master  hoop  in  Fig.  5.  These  blocks  are  securely 
nailed  to  the  floor  outside  of  the  line  with  the  square  end  exactly  on 
the  line.  They  cannot  be  fastened  too  securely  as  there  is  considerable 
strain  on  them  when  the  hoops  are  removed  from  the  master  hoop. 
The  blocks  should  be  spaced  every  fifteen  inches.  Next  these  blocks 
are  lined  with  the  first  layer  of  the  hoop  material,  breaking  joints  in 
the  center  of  the  blocks.     This  is  nailed  in  place  with  4d-nails.     The 


next  two  layers  are  put  in  the  same  way  except  that  the  end  of  the 
piece  is  started  about  half-way  between  two  blocks,  instead  of  at  a 
block  in  the  first  layer.  This  makes  a  tighter  fit  as  the  hoop  material 
has  a  tendency  to  straighten  out  near  the  ends  if  started  with  the  end 
at  a  block.  The  third  layer  should  be  put  in  with  6d-nails.  After 
putting-  in  the  three  layers  if  there  are  any  places  where  the  layers 
are  not  tight  together,  the  carpenter  should  go  around  and  drive 
small  nails  through  all  three  clinching  them  on  the  outside  by  driving 
against  a  heavy  sledge  hammer  or  something  similar.  It  is  also  a  good 
plan  to  drive  one  or  two  8d-nails,  between  each  two  blocks,  inclined 
through  the  lower  part  of  the  hoop  into  the  floor.     In  this  way  the 


Fig.  5. — Making  the  hoops. 


outside  of  the  hoop  can  be  drawn  accurately  to  the  line  at  all  points. 
Do  not  leave  any  nail  heads  protruding  on  the  inside  of  the  master 
hoop  as  the  other  hoops  must  be  slipped  out  of  the  master  hoop  when 
finished.  It  helps  greatly  in  removing*  the  hoops  to  rub  the  inside  of 
the  master  hoop  with  candle  grease  or  paraffin  to  make  it  smooth. 
Successful  hoop-making  depends  on  a  good  master  hoop. 

Next  a  number  of  swinging  blocks  or  sweeps  are  cut  from  the  same 
material  as  the  short  blocks,  about  three  feet  long.  Notice  them  inside 
of  the  hoop  in  Fig.  5.  A  hole  is  bored  with  a  small  bit,  to  fit  a  SOd-nail 
through  the  sloping  end  where  it  is  about  2  inches  thick.  In  placing 
these  sweeps  butt  the  square  end  tightly  against  the  inside  of  the 
master  hoop,  with  the  sloping  end  pointing  to  the  center  of  the  circle. 
Then  drive  a  30d-nail  through  the  hole  which  was  bored.  This  leaves 
the  sweep  free  to  swing  into  various  positions.  Put  one  of  these  about 
every  30  inches  around  the  master  hoop.     Before  beginning  to  make 


the  hoops,  it  will  facilitate  the  work  if  a  tool  be  made  for  springing 
the  hoop  material  into  place.  Get  half  of  a  leaf  of  a  broken  2  or 
2i/2-inches  wide  auto-spring  and  have  it  flattened  out  at  the  thick  end 
into  a  chisel-like  tool,  the  blade  tapering  off  gradually  to  a  thin  edge. 
The  end  should  be  about  as  wide  as  the  hoop  material.  Also  procure 
a  good  sound  block  of  hard  wood,  about  2  X  4  X  12  inches,  cut  square 
on  the  ends. 

Now  begin  to  build  up  the  hoop  by  first  swinging  all  the  sweeps 
in  the  master  hoop  to  the  right,  away  from  the  master  hoop.  Place 
a  piece  of  the  hoop  material  inside  of  the  master  hoop  with  the  smooth 
side  against  the  master  hoop.  Now  standing  inside  of  the  master  hoop 
begin  at  the  left-hand  end  of  the  piece  already  laid  in  and  swing  the 
sweeps  up  one  by  one  against  it  until  the  strip  is  held  tightly  against 
the  master  hoop.  The  next  piece  should  always  be  added  on  to  the 
right  hand  end  of  the  piece  just  put  in  and  the  sweeps  tightened  as 
before.  The  end  of  this  second  piece  (if  two  pieces  reach  around  as 
in  small  silos)  will  lap  over  the  end  of  the  first  piece  laid  down. 
Before  cutting  it  off  take  the  hardwood  block  you  have  provided  and 
placing  it  against  the  end  of  the  last  strip  laid  down  with  your  foot 
on  the  block  to  hold  it  firm,  drive  it  endwise  to  take  all  the  slack  out 
of  the  strip. 

When  the  strip  will  not  move  any  more,  mark  the  overlapping  strip 
to  cut  it 'off  about  %-inch  longer  than  it  apparently  will  go  in.  Loosen 
a  couple  of  the  sweeps  and  saw  the  strip  off  at  the  place  marked.  Now 
take  the  chisel-like  tool  and  placing  it  behind  the  end  just  sawed  off 
hook  it  on  to  the  end  of  the  other  strip.  Sit  down  on  the  floor  and  use 
your  foot  against  the  chisel  handle  as  a  lever  while  another  man  uses 
the  hard  wood  block  and  drives  the  strip  into  place.  You  cannot  get 
them  to  fit  too  tightly.  A  little  practice  will  show  you  how  much  to 
allow  when  sawing  off  and  how  to  use  the  chisel  to  advantage.  Now 
loosen  all  the  sweeps  and  put  in  the  next  layer  in  the  same  way, 
always  keeping  the  joints  several  feet  from  those  on  the  last  layer. 
After  three  layers  have  been  put  in  you  may  begin  nailing  with 
3d-nails,  only  using  a  few  nails  near  the  ends  of  the  pieces  where  they 
do  not^lie  down  smoothly.  Be  sure  you  never  use  any  nail  which  will 
reach  through  the  hoop  you  are  making  into  the  master  hoop.  All 
following  layers  may  be  nailed  in  as  you  go  with  enough  small  nails 
to  keep  them  up  tight.  When  the  last  layer  is  put  in  it  is  nailed  in 
with  large  nails  which  will  reach  almost  to  the  master  hoop.  A 
measurement  on  top  will  show  what  nails  to  use.  These  nails  should 
be  about  five  inches  apart  all  around  alternately  near  the  top  and 
bottom  of  the  hoop. 


9 

After  finishing  the  nailing  inside,  the  hoop  is  now  ready  to  be 
lifted  from  the  master  hoop.  A  mattock  (grubbing  hoe)  is  the  best 
tool  usually  available  for  this  work.  Raise  the  hoop  a  little  with  a 
bar  and  slip  the  blade  of  the  mattock  under,  then  follow  around 
shoving  sideways  on  the  handle.  This  will  raise  the  hoop  little  by 
little.  When  this  first  hoop  is  about  half  way  up  all  around,  the  two 
or  three  outside  joints  should  be  nailed  down  so  that  the  outside  layer 
will  not  spring  off  when  the  hoop  is  removed  from  the  form.  Before 
removing  it  farther,  take  a  steep  tape  and  carefully  measure  the  dis- 
tance around  the  outside  of  the  hoop  above  the  master  hoop.  This 
distance  is  divided  into  four  equal  parts.  Now  begin  by  making  a 
heavy  pencil  mark  across  the  top  of  the  master  hoop  at  any  starting 
point,  and  also  make  a  mark  across  the  top  of  the  hoop  at  the  same 


Top  of  Hoop  should 
&ecovere.dw\tktar 
or  asphalt 


Z&-H 


Fig.  6. — Detail  of  hoops. 


point.  Make  a  figure  (1)  on  the  outside  of  the  master  hoop  and  on 
the  inside  of  the  hoop  beside  these  marks.  Then  measuring  around 
the  hoop  from  this  point  make  the  same  marks  one-fourth  of  the  way 
around,  calling  these  marks  (2).  Always  measure  toward  the  right 
from  No.  1  when  standing  inside  the  hoop.  Do  the  same  for  the  third 
quarter.  When  the  fourth  quarter  point  is  reached  the  marks  should 
not  be  on  the  quarter  point  but  should  be  one-half  the  width  of  the 
door  to  the  right  of  this  point.  With  the  usual  20-inch  opening  this 
mark  should  be  10  inches  to  the  right  of  the  quarter  point  (when  you 
are  inside  the  hoop). 

Now  take  the  hoop  entirely  out  and  nail  it  on  the  outside,  just  as 
it  was  nailed  on  the  inside,  and  put  the  galvanized  iron  plates  over 
the  joints.  These  plates  being  about  y±  inch  wider  than  the  hoop, 
should  protrude  a  little  at  both  edges  so  that  it  may  be  crimped  over 
with  a  hammer  after  the  plate  is  nailed  on.  Use  the  large  nails  to 
put  them  on  with  about  ten  in  each  plate.  The  remaining  hoops  are 
all  made  in  the  same  way.  Be  sure  not  to  forget  to  mark  the  quarter 
points  on  the  top  of  each  hoop,  from  the  marks  on  the  master  hoop, 


10 

before  it  is  removed  from  the  form.  The  hoop  to  be  set  on  the  founda- 
tion should  have  about  three  strips  tacked  across  it  before  removing 
from  the  master  hoop,  to  keep  the  hoop  round  until  set. 

ERECTING  THE  HOOPS 

The  first  move  is  to  bolt  a  hoop  selected,  to  the  concrete,  taking 
care  to  get  the  marks  in  position  so  that  the  door  will  come  where 
desired.  Place  mark  No.  4  (the  one  which  was  not  at  the  quarter 
point)  at  the  right  hand  side  (when  standing  inside  the  silo)  of  the 
proposed  door  position.  Having  placed  the  hoop  in  the  right  position, 
begin  by  boring  a  hole  through  the  center  of  the  hoop  directly  over 
one  of  the  bolts.  Now  enter  this  bolt  a  little  way  into  the  hole  to  hold 
it  in  position  and  move  to  the  next  bolt.  After  getting  three  or  four 
entered,  go  all  around  and  be  sure  that  the  bolts  stand  about  in  the 
middle  of  the  hoop.  Then  proceed  and  bore  the  remaining  holes  and 
fasten  the  hoop  down  securely.  Before  putting  it  entirely  down,  it  is 
a  good  plan  to  pour  some  rich  cement  mortar  under  it  and  bed  the 
hoop  in  it  to  make  a  tight  fit. 

Marking  Off  and  Placing  the  Guides. — Take  three  good  straight 
pieces  of  2  X  3-inch  or  2  X  4-inch  material  about  18  feet  long  and  one 
piece  about  12  feet  long.  These  will  be  used  as  temporary  studs  to 
keep  the  hoops  in  line  before  the  staves  are  put  on.  Place  these  four 
pieces  side  by  side  with  ends  even  and  with  the  square  strike  a  mark 
across  them  to  show  the  level  of  the  bottom  of  each  hoop  when  it  is 
placed  in  position.  The  first  mark  should  not  be  2  feet  from  the 
bottom,  but  one-half  width  of  the  hoop  less  than  two  feet,  so  that  when 
the  bottom  of  the  hoop  is  at  the  mark  the  center  will  be  at  the  2-foot 
mark.  From  this  point  the  marks  will  be  two  feet  apart  up  to  the 
point  where  the  hoops  are  placed  further  apart.  Be  sure  to  have  the 
hoops  always  where  the  stave  joints  are  to  break,  so  placed  that  the 
staves  will  reach  to  the  middle  of  the  hoop.  In  a  30-foot  silo  the 
staves  would  break  at  the  12-foot  and  18-foot  levels,  so  the  middle  of 
the  hoops  should  be  accurately  at  12  feet  and  18  feet,  respectively.  If 
these  are  placed  accurately,  all  the  stave  material  can  be  cut  before 
erection  begins. 

The  three  long  temporary  studs  are  now  stood  up  outside  of  the 
bottom  hoop  at  three  of  the  four  quarter-marks  on  this  hoop.  Have 
the  studs  stand  on  the  concrete  and  have  the  same  edge  of  each  stud 
at  the  mark  on  top  of  the  hoop.  Now  take  a  20d-spike  and  drive  it 
through  the  stud  into  the  hoop,  drawing  the  stud  up  tightly  against 
the  hoop.  These  studs  are  plumbed  by  using  two  braces  at  right 
angles  fastened  to  stakes  driven  in  the  ground  as  shown  in  Fig.  8. 


11 


Before  erecting  the  last  stud,  place  four  more  of  the  hoops  on  top 
of  the  first  one,  taking  care  to  have  the  respective  numbers  on  the 
hoops  above  each  other.  This  will  save  moving  them  around  after- 
wards. After  placing  this  last  stud,  push  the  top  hoop  up  as  high  as 
you  can  reach  easily  and  drive  a  spike  in  each  stud  under  it  to  hold  it 
temporarily  in  place.  Then  raise  the  next  one  and  drive  the  spikes 
under  it  on  the  marks  which  are  just  below  six  feet.  Place  the  other 
two  hoops  similarly  above  the  4  and  2-foot  marks,  respectively. 

The  hoop  is  fastened  in  place  at  the  2-foot  level  with  the  marks 
on  this  second  hoop  exactly  above  the  similar  marks  on  the  first  hoop 
at  the  edge  of  the  studs.     This  is  fastened  by  driving  a  20d-spike 


Temporary  Cleats 
tofrciutate 

ERECTION  OF 
DOOR  FRAME 


Braces  maybe 
ejtherix30rix4 


ftRACINS  AT  %  P01NT5  '  ^RACING  AT  DOOR 

Fig.  7. — Detail  of  braces. 

through  the  stud  into  the  hoop.  The  mark  on  the  stud  should  now 
be  at  the  bottom  of  the  hoop  and  the  mark  on  the  hoop  at  one  edge 
of  the  stud.  The  next  two  hoops  may  be  similarly  fastened  in  place 
while  standing  on  the  ground.  Before  going  farther  some  more  tem- 
porary studs  of  1  X  4-inch  or  1  X  6-inch  material  are  stood  up  out- 
side the  hoops  half-way  between  each  pair  of  the  original  four  studs. 
These  should  be  nailed  securely  to  the  hoops  with  8d-nails.  Be  sure 
that  the  hoops  are  kept  at  the  same  height  at  these  last  studs  as  they 
are  at  the  first  four  studs.  They  are  often  quite  easily  shoved  up  or 
down  so  they  should  be  measured  each  time  before  making  them  fast. 
This  will  keep  each  hoop  level  all  around. 

The  Braces. — The  braces,  usually  of  2  X  3-inch  material,  are  set 
at  the  quarter-points  to  give  the  silo  rigidity.    Figs.  7  and  8  show  the 


12 

shape  and  location  of  the  braces.  These  braces  should  not  be  set 
flush  with  the  inside  of  the  hoops  as  they  will  lie  slightly  inside  of 
the  hoop  line  at  their  mid-point  and  interfere  with  the  laying  of  the 
staves.  It  is  a  good  rule  to  set  them  back  the  thickness  of  one  band 
%  inch  from  the  inside  of  the  hoop.  The  braces  should  be  nailed 
together  in  pairs  before  being  put  into  the  frame  as  they  are  then 
much  easier  placed.  The  cuts  along  the  line  where  the  braces  are 
nailed  together  should  be  at  such  an  angle  that  when  nailed  together 
in  pairs  the  braces  will  not  lie  in  one  plane  but  will  conform  to  the 
curve  of  the  hoops.  A  little  practice  will  show  how  to  cut  these  to 
make  them  fit  well.  The  point  of  the  braces  where  they  are  nailed 
together  should  not  be  nailed  to  the  hoop  until  after  the  staves  are 
laid  up  to  that  point.  The  short  studs  set  at  the  two  sides  of  the 
doorway,  20  inches  apart,  are  set  flush  with  the  inside  of  the  hoops 
and  securely  nailed  in  place. 

It  is  now  in  order  to  build  some  scaffolding  for  putting  up  the 
next  three  hoops.  Take  four  of  the  2  X  10-inch  or  2  X  12-inch  planks 
which  made  up  the  temporary  floor  and  lay  them  across  the  hoop  at 
the  6-foot  level,  as  shown  in  Fig.  8.  Always  try  to  have  them  resting 
near  to  one  of  the  studs  so  as  not  to  bend  the  hoops  out  of  place.  Now 
fasten  the  8-foot  hoop  in  place  as  the  others  were  and  take  up  another 
from  the  ground.  This  should  be  taken  over  the  top  of  the  low  stud 
and  fastened  in  place  before  another  is  pulled  up.  Move  the  scaffold 
up  when  you  can  not  work  easily  from  it.  Usually  it  is  moved  up 
every  six  feet. 

When  the  last  mark  on  the  short  stud  is  reached,  another  piece  of 
studding  is  added  on,  as  shown  in  Fig.  8,  and  the  marks  put  at  the 
correct  places  on  it.  Be  sure  in  adding  on  this  extension  to  the  stud 
that  the  new  piece  is  on  the  same  side  of  the  original  piece  as  the 
marks  on  the  hoops  are  on,  so  that  a  straight  line  will  be  formed 
from  the  bottom  of  the  silo  to  the  top  by  which  to  line  up  the  hoops 
correctly. 

This  stud  is  now  the  long  one  and  the  following  hoops  must  be 
taken  up  over  the  other  side  until  in  turn  new  ones  are  added  on  to 
them.  By  alternating  back  and  forth  no  difficulty  will  be  experienced 
in  taking  up  the  hoops.  After  the  first  seven  or  eight  are  up  it  will 
be  necessary  to  pull  them  up  with  ropes,  which  is  not  difficult  because 
of  their  lightness.     Continue  the  1  X  4-inch  studding  to  the  top  also. 

THE  STAVES 

Material. — The  staves  are  of  1  X  4-inch  tongue  and  groove  lumber, 
either  ordinary  pine  flooring  or  clear  redwood.    Specially  milled  staves 


13 


Fig.  8. — Erecting  the  hoops. 


14 


should  be  milled  full  on  the  outside  so  as  to  fit  well  when  laid  in  the 
circular  hoop. 

Placing  the  Scaffold. — Before  beginning  to  lay  the  staves  the  scaf- 
folding to  work  on  must  be  placed,  one  2  X  10-inch  or  2  X  12-inch 
plank  will  be  required  for  each  6  feet  of  height  of  the  silo.  At  the 
6-foot  level,  place  a  plank  with  one  end  in  the  doorway  and  the 
other  end  resting  on  the  hoop  near  the  next  quarter-point  to  the  right 
of  the  door.  Place  planks  every  6  feet  to  the  top  directly  above  each 
other. 


iN5!D£ 
YtB/ 


NAILING  toOCK  FOR 
STAVES  AT 

~  ">CH  HOOP 


THIS  CONSTRUCTION  MAY 
BE  USED  IN5TEAP0FTHE 
ONE  5H0W  A50VE  IF 
DESIRED 


Fig.  9. — Detail  of  door  frame  and  door. 

Start  the  first  stave  at  the  right  side  of  the  door  and  have  it  flush 
with  the  inside  edge  of  the  door  studs.  This  will  leave  a  20-inch  open- 
ing in  the  clear.  Run  this  stave  from  bottom  to  top  and  then  lay  the 
next  stave  breaking  joints  with  the  first  one.  Two  nails  should  be 
put  in  each  stave  at  each  hoop,  one  blind  nail  and  one  top  nail,  except 
at  the  ends  and  joints  of  the  staves  where  only  a  top  nail  is  needed. 
Have  the  man  on  the  top  scaffold  keep  sighting  down  the  staves  as 
they  are  laid  to  keep  them  in  true  perpendicular  line.  It  is  very  easy 
to  get  the  line  out  of  true  and  difficult  to  get  it  back  again.  A  plumb 
line  may  be  used  to  advantage. 

While  laying  the  staves  it  is  a  good  plan  to  tear  off  the  temporary 
studding  as  you  come  to  it,  and  if  the  staves  do  not  line  just  right, 
because  the  hoops  are  out  of  line,  the  studding  should  be  ripped  off 
several  feet  in  advance  of  the  staves  so  that  the  hoops  can  adjust 
themselves. 


15 

After  passing  the  first  set  of  braces  with  the  stave  laying,  shove 
the  point  of  the  pair  of  braces  in  against  the  staves  and  nail  them  fast 
to  the  hoop.  Do  this  at  each  set  of  braces  as  they  are  passed.  As  it 
becomes  necessary,  keep  moving  the  plank  around,  always  leaving  the 
one  end  in  the  doorway. 

When  the  staves  are  laid  about  three-fourths  of  the  way  around, 
the  scaffold  planks  can  no  longer  be  used  as  the  doorway  will  not  allow 
them  to  swing  farther.  They  will  then  be  taken  down  and  the  work- 
man must  stand  astride  of  the  hoops  to  finish  the  stave  laying.  This 
is  not  at  all  difficult  and  the  work  will  proceed  almost  as  rapidly  as 
when  the  planks  are  used.  Cut  the  last  stave  off  flush  with  the  door 
stud  as  the  first  one  was  started. 

THE  DOOEWAY 

The  doorway  is  continuous  from  top  to  bottom  adding  to  the  con- 
venience of  the  silo.  It  is  shown  in  detail  in  Fig.  10.  The  door  jambs 
are  nailed  on  as  shown  about  1  inch  back  from  the  edge  of  the 
doorway. 

THE  DOOES 

The  doors  are  made  of  two  thicknesses  of  flooring  with  tarred 
paper  between.  After  the  doors  are  made  up  they  are  sawed  down 
the  sides  on  the  correct  bevel  to  fit  the  door  jambs.  Each  door  fits 
directly  on  top  of  the  preceding  one,  the  two  layers  breaking  joints 
about  an  inch,  as  shown  in  Fig.  9.  When  putting  in  the  doors  as 
the  silo  is  filled,  it  is  well  to  seal  them  against  air-leakage  by  the  use 
of  soft  clay  mud.  Smear  the  top  of  the  last  door  and  the  sides  of  the 
one  being  put  in  with  it.  Then  after  it  is  in,  fill  the  crack  all  around 
the  door  with  the  clay  and  it  will  be  airtight  as  long  as  the  damp 
silage  is  against  it. 

THE  CHUTE 

A  chute  is  quite  necessary  and  should  extend  from  about  six  feet 
from  the  ground  to  the  top.  For  economy  it  can  well  be  built  of  plain 
barn  boards.     (See  Fig.  10.) 

THE  EOOF 

A  roof  on  a  silo  is  not  necessary,  although  it  will  protect  and 
strengthen  the  silo,  assist  in  preventing  the  silage  from  drying  out, 
keep  out  rain  and  birds,  and  improve  the  appearance  of  the  silo.  It 
may  be  framed  either  to  form  a  cone,  or  an  octagonal  pyramid,  as 


16 


shown  in  Fig.  11,  and  covered  with  shingles  or  prepared  roofing.     It 
is  often  convenient  to  build  the  roof  after  the  silo  is  filled. 


SPACING  OF  HOOPS  AND  LENGTH  OF  STAVES 

30-foot  silos : 

Total  of  thirteen  hoops,  6-ply  thick. 

First  seven  hoops  spaced  24  inches  between  centers  for  12  feet. 
Next  six  spaced  36  inches  between  centers  for  18  feet. 
Staves  made  of  18  and  12-foot  pieces  and  12  and  18-foot  pieces 
alternately. 


Prepared 
roofing 

egg     '   " 


Fig.  10. — Detail  of  roof  window  and  chute. 


17 


Fig.  11.— Detail  of  roof. 


18 

36-foot  silo: 

Total  of  fifteen  hoops,  6-ply  thick  for  10  and  12-foot  silo;  7-ply 

thick  for  14  and  16-foot  silos. 

First  seven  hoops  spaced  24  inches  between  centers  for  12  feet. 

Next  eight  hoops  spaced  36  inches  between  centers  for  24  feet. 

Staves  made  of  two  18-foot  pieces  and  three   12-foot  pieces 

alternately. 

42-foot  silo : 

Total  of  nineteen  hoops,  6-ply  thick  for  10  and  12-foot  silo ;  7-ply 
thick  for  14  and  16-foot  silo. 
First  ten  hoops  placed  24  inches  between  centers  for  18  feet. 
Next  five  hoops  placed  28%  inches  between  centers  for  12  feet. 
Next  four  placed  3  feet  apart  for  last  12  feet. 
Staves  made  of  18,  18  and  6-foot  pieces,  and  16,  14  and  12-foot 
pieces  alternately. 


TEEATING  THE  INSIDE  OF  SILO  AND  THE  HOOPS 

A  coat  of  tar  will  improve  the  tightness  of  the  silo.  The  less 
durable  wood  can  be  treated  with  creosote  oil  to  preserve  the  wood. 
The  silo  can  be  relined  on  top  of  first  lining  when  needed. 

The  top  of  the  hoops  where  exposed  to  the  weather  can  well  be 
coated  with  heavy  tar  to  protect  them  from  moisture. 


GUY  WIRES 

The  silo  is  a  light  structure  with  a  large  amount  of  surface  exposed 
to  the  wind.  To  protect  it  when  empty,  it  must  either  be  attached 
to  adjoining  buildings  or  thoroughly  guyed  to  posts  set  properly. 
Failure  to  do  this  will  often  result  in  the  destruction  of  the  silo. 


BILL  OF  MATERIALS 

The  following  bill  of  materials  does  not  include  plank  for  a  tempo- 
rary floor  on  which  to  make  the  hoops  or  several  pieces  needed  for 
scaffolding.  The  temporary  floor  should  be  about  two  feet  larger 
than  the  diameter  of  the  hoops.  One  2  X  10  or  2  X  12-plank  for 
scaffolding  will  be  needed  for  each  six  feet  of  height. 


19 


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MATERIAL  FOE 


20 


WOOD-HOOP  SILOS—  (Continued) 
Diameters 


Height 

10  feet 

12  feet 

14  feet 

16  feet 

Prepared  roofing 

2  squares 

2  squares 

3  squares 

3  squares 

Door    jambs    made    of 
2"  X  6"  cut  as  shown 
in  Fig.  10. 

30' 
36' 

60  linear  ft, 
72      "       " 
84      "       << 

,     All  diameters  same. 
a            a             it 

Nails :      The      8d-nails 
should  be  galvanized. 
The   remainder    com- 
mon wire. 

30' 

Lbs. 

7 
53 

8 

5 

d. 

20 
8 
6 
4 

Lbs. 

7 
61 
10 

6 

d. 

20 
8 
6 
4 

Lbs. 

7 

69 

12 

7 

d. 

20 
8 
6 
4 

Lbs. 

7 
77 
14 

8 

d. 

20 
8 
6 
4 

36' 

8 
73 
10 

7 

20 

8 
6 

4 

8 
81 
12 

8 

20 
8 
6 
4 

8 
89 
14 

9 

20 
8 
6 
4 

8 
97 
16 
10 

20 
8 
6 
4 

42' 

9 
83 
11 

8 

20 
8 
6 
4 

9 
91 
13 

9 

20 

8 
6 

4 

9 
99 
15 
10 

20 
8 
6 
4 

9 

107 

17 

11 

20 
8 
6 
4 

One  piece  of  No.  26  galvanized  iron,  12  inches  long  and  a  little  wider  than  the 
hoop  material,  for  every  outside  joint  on  the  hoops.     If  two  pieces  reach  around  a 
hoop,  then  two  pieces  of  iron  will  be  needed  for  each  hoop,  etc.     (See  Fig.  6.) 
Three  or  four  guy  wires  with  two  eye-bolts  for  each  should  be  provided,  viz.: 
36  feet  long  for  30-foot  silo; 
42  feet  long  for  36-foot  silo; 
48  feet  long  for  42-foot  silo. 
Five  or  six  strands  of  No.  9  wire  make  a  good  guy  wire. 
Posts  will  be  needed  to  which  to  attach  guy  wires. 


